Salts are ionic compounds which result from the interaction (neutralization) of an acid and a base. Salts are composed of cations and anions which interact so that an electrically neutral state is maintained. Anions can be inorganic (such as Cl−) or organic such as acetate (CH3COO−). Aqueous solutions containing dissolved salts (electrolytes) are able to conduct electricity due to the dissociated state of the anion and cation pairs in an aqueous environment. Oligonucleotides are polyanions and have been previously thought to only behave as salts where their cation counterparts exist in solution in a dissociated state.
The administration of ONs to human patients has typically been accompanied by several generalized side effects not related to the nucleotide sequence present. These include anti-coagulation (elevation of pro-thrombin time or PTT time) of the blood (Kandmimlla et al., 1998, Bioorgan. Med. Chem. Let., 8: 2103; Sheeban et al., Blood, 1998, 92: 1617; Nicklin et al., 1197, Nucleosides & Nucleotides, 16: 1145; Kwoh, 2008, Antisense Drug Tech. 2nd Ed., p 374) and injection site reactions or ISRs (induration, inflammation, tenderness and pain) with subcutaneous administration (Webb et al., 1997, Lancet, 349: 9059; Schrieber et al., 2001, Gastroenterol., 120: 1339; Seawell et al., 2002, J. Pharmacol. Exp. Therap., 303: 1334; Kwoh, 2008, Antisense Drug Tech. 2nd Ed., p 383; Raal et al., 2010, Lancet, 375: 998). The anti-coagulation effects are thought to be mediated by non-sequence specific interaction with proteins of the coagulation cascade. As ONs have been shown to possess immunostimulatory properties (via Toll-like receptor or TLR-mediated cytokine induction), ISR's have typically been attributed to the requirement for high concentration ON administration in a small volume (typically 1 cc) for subcutaneous (SC) injection, which is thought to lead to local inflammation at the injection site.
With the advent of nucleic-acid based therapy in recent years, the increased numbers of ON-based compounds in clinical development has increased. Historically most ON dosing regimens have employed multiple doses in a week or single weekly doses which must be given parenterally due to the poor oral bioavailability of ONs. Since intravenous infusion of ONs is typically dose and rate limited by reactivity (fever, shivering, weakness) and would be logistically demanding in a chronic dosing scenario, more recent clinical application of ONs have used the subcutaneous (SC) route of administration. This leads to minimal systemic dosing side effects but is typically accompanied by injection site reactions of varying degrees of severity (as described above) which also limit the dosing achievable by this route of administration.
It would therefore be useful and desirable to be provided with an ON formulation which would mitigate reactivity during either IV or SC routes of administration. Furthermore, while the anti-coagulation effects of ON administration are considered minimal, it would also be useful to neutralize this side effect of ONs to provide for a greater margin of safety in human and non-human subjects.
There is thus a need to be provided with an improved ON formulation.